Friday 13th April was unlucky for Wellington, with the tail of a cyclone forecast to whip down the north island of New Zealand and ruin the Easter holidays. So I didn't resent working indoors, tucked away from the wet and the wind inside Peter Jackson's private cinema, where the dialogue for The Lord of the Rings is being "cleaned up" for the final version of the trilogy's first movie, due to be delivered for inspection by New Line's executives in Hollywood early in June.

I had the call a month or so ago in London, where I have been enjoying a prolonged break from professional life since the principal photography ended just before Christmas. While I lazed the winter away, Peter Jackson and his diminished cohorts have laboured through a hot New Zealand summer. Some pick-up shots kept Viggo Mortensen (Aragorn) filming through most of January. The WETA digital department have 120 technicians perfecting the special effects, whilst Peter and his editors have been shaping the first film and fitting together the story of the Fellowship's journey to Mordor, where the Ring was forged and must be destroyed.

The Wellington film studios not being soundproofed, almost all of the dialogue has had to be replaced. Two of the co-screenplay-writers Fran Walsh (Mrs. Jackson) and Philippa Boyens have been in charge of the ADR (Additional Dialogue Recording). Already, in an underground sound studio off Wardour Street in London, Sean Bean (Boromir), Ian Holm (Bilbo) and Christopher Lee (Saruman) have added a fresh soundtrack to their scenes. Why was I being brought back to Wellington?

Not just to do the ADR. The very opening of the film due this December was to be changed. Its original prologue has been abandoned and the backstories of Isildur and of Smeagol who both found and lost the Ring are now to be told once Bilbo, the adventurer from Tolkien's The Hobbit has been introduced. In Bag End, we will see Bilbo starting to write his memoirs. Gandalf's arrival in Hobbiton for Bilbo's 111th birthday party of magnificence now opens the movie just as it opens the first book but it has been expanded to help with the exposition. Hence the need for extra filming. A prologue, with its stash of names and facts, can unnerve audiences and I am relieved that ours has gone. I was happy to be back filming, even if only for a few days amongst my main task of giving Gandalf his voice.

I had half-hoped to be shown the current version of The Fellowship of the Ring but there still isn't anything complete enough to be called a film  rather an over-long string of scenes, without music, special effects or polished editing. But it's been greatly reassuring, before each ADR session, to be able to view the Gandalf scenes and to see how excitingly the story is being told and how movingly the characters relate to each other as their adventures proceed from Hobbiton to Mordor. At the end of this first film Frodo and Sam are separated from the rest and row across the river, destination Mount Doom  on even a scratchy video, Elijah Wood and Sean Astin are heart-breaking and couldn't be better  I thought.

I reckoned without Howard Shore's music, some of which is being recorded by the New Zealand Symphony Orchestra and a male choir especially assembled for the movie. Last week I dropped in to watch them play and sing. It was the end of a long day for the musicians but their enthusiasm for Howard and the whole project was evident.

I sat behind Peter Jackson huddled over a monitor showing the footage of Sam and Frodo in their rowboat. As the majestic Fellowship theme soared over the pictures and a plaintive flute and drums enchanted the ear, I heard and saw the first moment of completed film. Trust me: it is magnificent.

p.s. I'm sorry the above is a little late but what with travelling and Cannes (of which more soon) even wizards can get behind with things. Peter Jackson has now cut the new opening to The Fellowship of the Ring as we must get used to calling the first movie in the trilogy. He was very pleased with the changes, which coming from the master storyteller, is just what I expected.  Ian McKellen, May 2000